code: def __init__(self):
      self.A = torch.tensor([[0.0, 1.0], [-1.0, 0.0]])
      self.B = torch.tensor([3.0, 3.0])
      self.sigma_z = torch.tensor(1.0)
      self.sigma_y = torch.tensor(1.0)
  
imports: import pytest
  import torch
  import pyro
  import pyro.distributions
  import pyro.poutine
  from pyro.infer import SMCFilter
  from pyro.infer.smcfilter import _systematic_sample
  from tests.common import assert_close
label_desc: Use image node_id 1 to create a new HarmonicModel object  with example: obj = HarmonicModel()